We plan to continue the development of general methods which will be generally applicable in the synthesis of macrolides, including the prototypes of the major subclasses within the group, partly in the hope that the presently obscure relationships between chemical structure and physiological activity in this important group might be elucidated. In the immediate future we shall be mainly concerned with the reduction to practice and refinement of methods we have developed for the synthesis of the entire main chain of the erythromycin nucleus, with all its ten asymmetric centers properly oriented both in the relative and absolute senses. Further, we shall take up studies on closure of the lactone ring, and attachment of sugar units, to complete the synthesis of erythromycin.